Transmission, in particular an automated power-branched multi-speed gearing

ABSTRACT

A transmission ( 1 ) is proposed, especially an automated power-split multi-speed transmission, comprises at least three power branches (P 1 , P 2 , P 3 ), which are each connected to a shaft ( 2, 3, 4 ) of a downstream planetary gearset ( 5 ) and are configured with at least one partial transmission ratio (i 1 , i 2 , i 3 ). Each power branch (P 1 , P 2 , P 3 ) comprises a control element (S 1 , S 5,  S 6 ) for connecting the power branches (P 1 , P 2 , P 3 ) to a power flow of the transmission ( 1 ) at a partial transmission ratio (i 1 , i 2 , i 3 ). At least one of the shafts ( 3, 4 ) of the planetary gearset ( 5 ) interacts with an additional control element (S 2 , S 4 ), via which the shaft ( 3, 4 ) can be supported in relation to a housing ( 6 ). An additional control element (S 3 ) is arranged between two shafts ( 3, 4 ) of the planetary gearset ( 5 ) which, in its closed state, blocks the planetary gearset ( 5 ).

This application is a national stage completion of PCT/EP2004/003274filed Mar. 27, 2004 which claims priority from German Application SerialNo. 103 15 313.6 filed Apr. 4, 2003.

FIELD OF THE INVENTION

The invention relates to a transmission, especially an automatedpower-split multi-speed transmission, having at least three powerbranches.

BACKGROUND OF THE INVENTION

Automated manual transmission systems that are primarily based on theprinciple of conventional manual shift transmissions having acountershaft design are generally known from practice, where shifting isperformed with the aid of control elements configured as synchronizingelements, which are characterized by the fact that they require littlespace. In contrast to this, the power-determining elements of acountershaft transmission, which due to their long life and highefficiency are generally configured as spur gears, require a lot ofspace, which is often limited the case of passenger vehicles.

Transmission concepts having a substantially more compact design areautomatic powershift transmissions with planetary gearsets, which mayadditionally comprise an internal torque split design. While thesetransmissions, due to their compact design, require relatively littlespace, it is disadvantageous with this type of transmission that thecontrol elements, such as friction clutches and friction brakes, have tobe dimensioned relatively large and be actuated hydraulically. Thisresults in considerable drag losses and an accordingly high level ofactuating energy, which influences the efficiency of the transmissionnegatively.

Furthermore, transmission types are known from practice which attempt tocombine the advantages of the countershaft transmissions with respect totheir small control elements and the advantages of the automatedpowershift transmissions comprising planetary gearsets with respect totheir compact gearing in that a downstream planetary gearset is providedin a countershaft transmission, thus creating a range-changetransmission with purely geometrical ratios. The problem here is, amongother things, that the ratios in lower gears are very small, while theyare very large in higher gears, making driving the passenger vehiclemore difficult.

A combination of features of the above-described transmission types isdisclosed in U.S. Pat. No. 5,013,289 with a transmission comprising acountershaft transmission area and two planetary gearsets. Three powerpaths are provided between a gear input shaft and an output or arrangedcoaxially thereto, in which the gear ratio can be changed by way of apower shift. By providing three power paths that may be connected to theplanetary gearsets, six forward gears can be implemented with relativelyfew control elements.

The disadvantage here, however, is that the power shift requires the useof multi-disk clutches, resulting in correspondingly high expenses forthe design, the hydraulic control and regulation, and that the spacerequirement of the transmission has not been optimized with respect tothe gears that can be shifted with the transmission.

It is, therefore, the object of the present invention to provide atransmission, especially an automated power-split multi-speedtransmission, which has been improved compared to the prior art in thatit can have a compact design even with a higher number of shiftablegears and can be implemented in a simple layout with little spacerequirement and which is characterized by good driving behavior.

SUMMARY OF THE INVENTION

When using the transmission, according to the invention, which ispreferably configured to incorporate countershaft and power-splitdesigns and comprises at least three power branches—with at least onecontrol element and at least one partial transmission ratio,respectively—and the planetary gearset, the transmission can be shiftedeasily and pleasantly, since such a transmission can be implemented withthe required gear steps.

Additionally, according to the invention, the combination of the partialtransmission ratios arranged in a power branch and the planetary gearsetadvantageously results in the possibility of implementing themulti-speed transmission with the largest possible number of gear steps,which are, in turn, achieved with the lowest possible amount oftransmission components.

This advantageously leads to the fact that the transmission, accordingto the invention, has smaller outer dimensions compared toconventionally designed multi-speed transmissions and is characterizedby a lower overall weight, which consequently results in a better fueleconomy when using the multi-speed transmission in a motor vehicle.

Beyond that, it is advantageous that in the case of simple shifts in themulti-speed transmission, essentially only one disclosed control elementis closed in each case, and a closed control element is disclosed fromthe power flow of the transmission, according to the invention, whichprevents range shifts that are critical in terms of shifting quality,where several control elements of a transmission have to be actuatedsimultaneously, nearly completely.

Additionally, compared to the transmissions known from the prior art,the transmission, according to the invention, has the advantage thatwith the transmission at least one gear or an overall gear ratio can beimplemented at which the driving torque can be guided directly throughthe transmission, i.e. without losses in the gearing of thetransmission.

This is accomplished in that an additional control element which, in itsclosed state blocks the planetary gearset, is arranged between twoshafts of the planetary gearset.

Moreover, the arrangement of the additional control element, accordingto the invention, leads to the fact that compared to transmissions knownfrom the prior art, more gear ratios can be implemented withoutadditional gear wheel steps so that the number of possible shiftablegear steps is optimized with respect to the space requirement of thetransmission, according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings in which:

FIG. 1 is a basic diagram of a transmission according to the invention;

FIG. 2 is a wheel diagram of the transmission illustrated in principlein FIG. 1;

FIG. 3 is a schematic diagram and a gear ratio series for a transmissionaccording to the invention configured as an 8-gear transmission, and

FIG. 4 is a schematic diagram and a gear ratio series for a transmissionaccording to the invention configured as a 9-gear transmission.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, a basic diagram of a transmission 1 configured as anautomated, power-split, multi-speed transmission is shown, whichcomprises three power branches P1, P2 and P3. The power branches P1 toP3 are connected to a shaft 2, 3, 4 of a planetary gearset 5,respectively. Additionally, each of the power branches P1 to P3comprises a partial transmission ratio i1, i2 and i3 as well as acontrol element S6, S5 and S1, respectively. The power branches P1 to P3can be connected to a power flow of the transmission 1 by way of thecontrol elements S6, S5 and S1.

Additionally, the two shafts 3 and 4 of the planetary gearset 5 can besupported in relation to a housing 6 of the transmission 1 by way ofcontrol elements S4 and S2 or can be fixed torsion-resistant in thehousing 6 of the transmission 1.

Beyond that a control element S3, which in its closed state blocks theplanetary gearset 5, is arranged between the two shafts 3 and 4 of theplanetary gearset 5 so that a driving torque applied by a gear inputshaft 7 can be guided directly to a gear output shaft 8 at an overallgear ratio of i_ges=1 when the control element S2 is closed and thecontrol element S3 is closed.

With the three specified gear ratios i1, i2 and i3 and the controlelements S1 to S6, as illustrated in the diagrams 24 in accordance withFIG. 3 and FIG. 4, advantageously eight or nine gear steps for forwardtravel can be shifted, which are implemented as progressive ratios for amore comfortable driving experience. A reverse gear can be implementedeither through an additional spur gear step with integrated rotationalspeed reversal or by way of a forced rotational speed reversal in theplanetary gearset 5 by switching the control elements S1 to S6 in asuitable fashion.

FIG. 2 shows a wheel diagram of the transmission 1, with thetransmission 1 comprising a transmission structure configured as acountershaft transmission and the planetary gearset 5 implemented as asummation gear and arranged downstream from the countershafttransmission area. The transmission 1 is equipped with a main shaft 9 inthe area of its countershaft transmission, with a countershaft 10 beingarranged parallel thereto, on which three spur gears 11, 12, 13 engagingwith the spur gears 14, 15 and 16 are arranged.

The spur gear 14 is connected torsion-resistant to the gear input shaft7 and constantly drives the countershaft 10 during operation of thetransmission 1. Moreover the gear input shaft 7 is connected to the mainshaft 9 of the transmission 1 in the closed state of the control elementS1.

The planetary gearset 5 in the present example is configured as a4-shaft planetary gearset, which is composed of two minus planetarygearsets 5A and 5B. A planet carrier 17 of the first minus planetarygearset 5A is connected to an internal gear 18 of the second minusplanetary gearset 5B. A planet carrier 19 of the second minus planetarygearset 5B is connected to an internal gear 20 of the first minusplanetary gearset 5A and the gear output shaft 8.

As an alternative to the latter version of the planetary gearset, inanother construction of the transmission, according to the invention, itmay also be provided that the planetary gearset is combined from twoother planetary gearsets. The planetary gearset may be constructed,e.g., as a Ravigneaux planetary gearset.

The main shaft 9, which is connected to the planet carrier 17 of thefirst minus planetary gearset 5A, is connected in the closed state ofthe control element S2 such to the housing 6 of the transmission 1 thatthe main shaft 9 and hence also the carrier or planet carrier 17 of thefirst minus planetary gearset 5A are arranged torsion-resistant in thehousing 6.

In the closed state of the control element S3, the main shaft 9 isconnected, via a hollow shaft 21, to a sun gear 22 of the first minusplanetary gearset 5A so that the sun gear 22 and the carrier 17 of thefirst minus planetary gearset 5A are connected non-rotably to eachother, and the planetary gearset 5 is blocked and revolves as a rigidunit.

In the closed state of the control element S4, the hollow shaft 21, andhence the sun gear 22 of the first minus planetary gearset 5A, areconnected fast to the housing 6, with the gear ratio formed by themutually engaging spur gears 12 and 15 being connected to the power flowof the transmission 1 when the control element S5 is closed.

By way of the control element S6, another spur gear ratio, which isformed by the mutually engaging spur gears 13 and 16, is connected tothe power flow of the transmission 1. This means that in the closedstate of the control element S6, the driving torque applied by thecountershaft 10 is directed on a sun gear 23 of the second minusplanetary gearset 5B.

With appropriate actuation of the control elements S1 to S6 gear, inputtorque is directed to one of the power branches P1, P2 or P3 or, at thesame time, via two of the three power branches P1 to P3 when thepower-split mechanism is activated. Each of the power branches P1 to P3is connected to a power flow of the transmission 1, as needed, ordisconnected therefrom with the aid of the associated control elementS6, S5 or S1 at its partial transmission ratio i1, i2 or i3.

The power paths P1 to P3 which, in the present example, are providedwith a partial transmission ratio, may also be configured withtransmission structures that have more than one partial transmissionratio in another embodiment of the invention.

When using the above-described embodiment of the transmission combinedwith the switching logic explained hereinafter, many gear steps oroverall gear ratios of the transmission 1 can be implemented while, atthe same time, keeping the number of gear ratio steps low, thusproviding a very beneficial transmission concept in terms of space.

FIG. 3 and FIG. 4 illustrate schematic diagrams 24 reflecting thecorrelation between the individual gears for forward travel “1” to “8”or “1” to “9” and a reverse gear “R1” of the transmission 1 from FIG. 1and the shifting states of the control elements S1 to S6.

The schematic diagrams 24 are prepared in the form of tables, theleft-hand column of which list the individual gears “1” to “8” or “1” to“9” and “R1” of the transmission 1. The top lines of the schematicdiagrams 24 list the individual control elements S1 to S6, an overallgear ratio i_ges of the transmission 1 and a progressive ratio phi,which is formed from the quotient of the values of two successiveoverall gear ratios.

The schematic diagram 24 in FIG. 3 in conjunction with the basic diagramof the transmission 1 illustrated in FIG. 1 shows, for example, that thecontrol elements S4 and S6 are closed or connected for shifting thefirst gear “1” or the first overall gear ratio i_ges of the transmission1. In this operating mode of the transmission, a driving torque isdirected from the gear input shaft 7, via the spur gears 14 and 11, tothe countershaft 10 and, via the spur gears 13 and 16, to the sun gear23 of the second minus planetary gearset 5B. Thereafter it is forwardedto the gear output shaft 8.

In this state of the transmission 1, the driving torque of the gearinput shaft 7 is directed to the planetary gearset 5, via the powerbranch P1 illustrated in FIG. 1, since the power branch P1 is connectedto the power path of the transmission 1, via the closed control elementS6. At the same time, the shaft 3, which in FIG. 2 is the sun gear 23 ofthe second minus planetary gearset 5B, is connected torsion-resistant tothe housing 6.

In the present case, the partial transmission ratio i1 of the powerbranch P1 is formed by the mutually engaging spur gears 14 and 11 at apartial transmission ratio ik and a gear ratio of the spur gears 16 and13. The overall gear ratio i_ges in the first gear “1” of thetransmission 1 has a value of 6.696 due to the sun gear 23 of the secondminus planetary gearset 5B, the sun gear being held torsion-resistant bythe closed control element S4 and the developing gear ratio in theplanetary gearset 5.

During an upshift, starting from gear “1” into gear “2” of thetransmission 1, the control element S6 remains closed and the controlelement S3 is connected while, at the same time, the control element S4is disconnected or disclosed. Connecting the control element S3 causesthe planetary gearset 5 to become blocked or locked so that the elementsof the planetary gearset can no longer rotate in relation to each otherand the planetary gearset 5 revolves as a unit in the housing 6 nearlyloss-free with the exception of the bearing losses.

In the closed state of the control element S3, the shaft 3 and the shaft4 of the transmission 1, which in FIG. 2 are the sun gear 22 of thefirst minus planetary gearset 5A connected to the hollow shaft 21 andthe planet carrier 17 of the second minus planetary gearset 5B connectedto the main shaft 9, are connected to each other. The driving torque ofthe gear input shaft 7 is applied to the countershaft 10, via the spurgears 14 and 11, at the gear ratio ik when the control element S1 isclosed and is then applied directly to the gear output shaft 8, via thespur gears 13 and 16 and the blocked planetary gearset 5, due to theclosed control element S6.

The partial transmission ratio i1 of the connected power branch P1, inturn, is formed from the gear ratio ik and the gear ratio between thespur gears 13 and 16, leading to an overall gear ratio i_ges of 3.973due to the blocked planetary gearset 5. This results in a progressiveratio phi of 1.685 between the first gear “1” and the second gear “2” ofthe transmission 1.

To shift the reverse gear “R1”, the control element S2 and the controlelement S5 are closed simultaneously, as illustrated in the schematicdiagram 24 in accordance with FIG. 3 and FIG. 4, thus directing thedriving torque via the power branch P2 through the transmission 1 in thedirection of the gear output shaft 8 and, on the other hand, achieving arotational direction reversal in the planetary gearset 5 to implementthe reverse gear “R1”.

During an upshift, starting from gear “2” into gear “3” of thetransmission 1, the control element S6, in turn, remains closed and thecontrol element S5 is connected to the power flow of the transmission 1.At the same time, the control element S3 is disconnected. This way thedriving torque of the gear input shaft 7 is directed through thetransmission 1, via the two power branches P1 and P2 at their partialtransmission ratios i1 and i2, with the split driving torque being addedup in the planetary gearset 5 and subsequently forwarded to the gearoutput shaft 8.

In this operating state of the transmission 1, the gear input torque isdirected via the spur gears 14 and 11 at the gear ratio ik to thecountershaft and from there via the spur gears 12 and 15 and their gearratio to the sun gear 22 of the first minus planetary gearset 5A. At thesame time, part of the driving torque is directed from the countershaft10, via the spur gears 13 and 16 and their gear ratios, to the sun gear23 of the second planetary gearset 5B. In the planetary gearset 5 thetwo parts of the driving torque are added up and forwarded to the gearoutput shaft 8.

The partial transmission ratio i2 of the connected power branch P2 isformed from the gear ratio ik and the gear ratio resulting from theratio of the number of teeth of the spur gears 12 and 15. The partialtransmission ratio i1 of the power branch P1 is composed of the gearratio ik and the gear ratio between the spur gears 14 and 11. This stateof the transmission 1 results in an overall gear ratio i_ges of 2.602 ofthe gear “3”. The progressive ratio phi between the second gear “2” andthe third gear “3” of the transmission 1 is 1.527.

During a further upshift from the third gear “3” to the fourth gear “4”,the control element S6 is disconnected and the control element S3 isclosed so that the gear input torque is directed, via the power branchS2 and the blocked planetary gearset 5, to the gear output shaft 8causing, on one hand, no torque split to exist in the transmission 1and, secondly, avoiding power loss in the planetary gearset 5 due to thedirect transmission of the gear input torque at the partial transmissionratio i2, which then also simultaneously represents the overall gearratio i_ges.

When the fifth gear “5” has been closed in the transmission 1, thecontrol element S1 and the control element S6 are closed so that thegear input torque is directed, via the power paths P1 and P3, across apower split through the transmission 1 and directed in the summatedstate in the planetary gearset 6 (which is not blocked in this case) tothe gear output shaft 8.

In order to implement the sixth gear “6” in the transmission 1, thecontrol element S1 and, at the same time, the control element S3 areclosed so that a gear input torque of the gear input shaft 7 is directedby way of the control element S1, via the power branch P3, to the shaft4 of the planetary gearset 5. The closed control element S3, in turn,causes the planetary gearset 5 to be blocked and the gear input torqueto be directed from the gear input shaft 7 directly, i.e., at an overallgear ratio i_ges equal 1.0, and nearly free of losses through thetransmission 1 to the gear output shaft 8. Consequently, the partialtransmission ratio i3 of the power branch P3 has a value of 1 in thepresent case.

Compared to familiar transmissions from the prior art, theabove-described shifting logic and the associated alternating conductionof the driving torque, via one or simultaneously via two of the threepower branches at the different partial transmission ratios incombination with the additional control element for blocking theplanetary gearset 5, leads to the fact that the same number of gearsteps can be implemented with fewer wheel planes. Thus the transmission,according to the invention, has significantly smaller outer dimensions;consequently, a lower overall weight and, moreover, considerably lowermanufacturing costs at the same power capacity.

Moreover, compared to the standard transmissions known from the priorart, according to the invention, the transmission is characterized byhigher efficiency since the driving torque is transmitted with severalgear steps of the transmission directly through the transmission, i.e.,with a blocked planetary gearset 5, to the gear output shaft 8.

Additionally, the progressive ratio of the individual overall gearratios of the transmission 1 offers a better possibility to adjust theavailable torque to the required torque than is the case withgeometrically stepped transmissions since conventional range-changetransmissions generally have equally large gear transitions due to theirgeometrically stepped design.

The control elements S1 to S6 of the transmission 1 are configured inthe present case as familiar synchronizing devices, which are providedwith a friction clutch or brake component to compensate for rotationalspeed differences in the transmission. After the synchronizing step, thecomponents of the power branches or of the transmission 1, which areconnected to each other torsion-resistant, are positively coupled by wayof a positive fitting clutch or brake component of the control elementsS1 to S6.

Alternatively in another advantageous embodiment of the transmission,according to the invention, it may also be provided that the controlelements S1 to S6 are configured as friction control elements, such asmulti-plate clutches or multi-plate brakes; the transmission 1 thenbeing configured as a powershift transmission with which up- anddownshifts can be performed under load, i.e., without interruption ofthe torque flow.

The control elements can be arranged in front of or behind therespective gear step which, in the present case, is configured as a spurgear step and is connected or disconnected via the control elements. Thecloser the control elements are positioned to the gear steps that aresupposed to be connected, the smaller the rotating mass of thetransmission components involved in the shift that needs to besynchronized by the control elements.

Additionally, in another advantageous further development of thetransmission, according to the invention, it can be provided that adriving element is provided in a powertrain of a vehicle or motorvehicle, the driving element being one of the control elements of thetransmission configured as power shift elements or a separate component,such as a hydrodynamic torque converter, a dry clutch or an electricmotor that is actively connected to an arbitrary shaft of themulti-speed transmission.

Especially when the driving element is separately configured as anelectric motor, a driving torque that is required to start moving iseither generated by the electric motor or a driving torque applied by adriving machine is supported by the electric motor such that, at theoutput of the vehicle, the driving torque required to start moving isapplied.

If the three power paths P1 to P3 are configured with three transmissionstructures having several transmission structure ratios and beingimplemented in any of the power branches P1 to P3 instead of with thepartial transmission ratios i1 to i3, the number of gears that can beimplemented with the transmission 1 can be increased significantly. Thetransmission structure ratios in the individual transmission structurescan be prepared and closed without load before connecting the respectivepower branch so that the shift of the various transmission structuregear ratios in the transmission structures can be performed withpositive fitting control elements, which are inexpensive andspace-saving.

Connecting the power branches to the power flow of the transmission,according to the invention, can independently advantageously beaccomplished with power-shift friction control elements, such asmulti-plate clutches, under load without interrupting the torque flow.

As an alternative to the embodiment of the inventive transmissionillustrated in FIG. 2, the countershaft area of the transmission may beconfigured with at least two equal countershafts arranged parallel tothe main shaft in the housing, allowing the transmission to be designedeven smaller, lighter and at a lower cost.

REFERENCE NUMERALS

-   1 transmission-   2-4 shafts of the planetary gearset-   5 planetary gearset-   5 a first minus planetary gearset-   5 b second minus planetary gearset-   6 transmission housing-   7 gear input shaft-   8 gear output shaft-   9 main shaft-   10 countershaft-   11-16 spur gears-   17 planet carrier of the first minus planetary gearset-   18 internal gear of the second minus planetary gearset-   19 planet carrier of the second minus planetary gearset-   20 internal gear of the first minus planetary gearset-   21 hollow shaft-   22 sun gear of the first minus planetary gearset-   23 sun gear of the second minus planetary gearset-   24 schematic diagram-   P1-P3 power branch-   i1, i2, i3, ik partial transmission ratio-   S1-S6 control element

1-12. (canceled)
 13. An automated power-split multi-speed transmission(1), comprising at least a first, a second and a third power branch (P1,P2, P3), the first power branch (P1) is connected to a first shaft (2),the second power branch (P2) is connected to a second shaft (3) and thethird power branch (P3) is connected to a third shaft (4), the first,the second and the third shafts (2, 3, 4) communicate with a downstreamplanetary gearset (5), the first shaft (2) is configured with at least afirst partial transmission ratio (i1), the second shaft (3) isconfigured with at least a second partial transmission ratio (i2) andthe third shaft (4) is configured with at least a third partialtransmission ratio (i3), the first power branch (P1) has a first controlelement (S6) for connecting the first power branch (P1) to a power flowat the first partial transmission ratio (i1), the second power branch(P2) has a second control element (S5) for connecting the second powerbranch (P2) to a power flow at the second partial transmission ratio(i2), and the third power branch (P3) has a third control element (S1)for connecting the third power branch (P1) to a power flow at the firstpartial transmission ratio (i3), and at least one of the second andthird shafts (3, 4) of the planetary gearset (5) interacting with anadditional control element (S2, S4), via which the at least one of thesecond and third shafts (3, 4) can be supported in relation to a housing(6) and a third additional control element (S3), the third additionalcontrol element (S3), in a closed state, blocks the planetary gearset(5), being arranged between the second and third shafts (3, 4) of theplanetary gearset (5), the transmission (1) having eight forward gears.14. An automated power-split multi-speed transmission (1), comprising atleast a first, a second and a third power branch (P1, P2, P3), the firstpower branch (P1) is connected to a first shaft (2), the second powerbranch (P2) is connected to a second shaft (3) and the third powerbranch (P3) is connected to a third shaft (4), the first, the second andthe third shafts (2, 3, 4) communicate with a downstream planetarygearset (5), the first shaft (2) is configured with at least a firstpartial transmission ratio (i1), the second shaft (3) is configured withat least a second partial transmission ratio (i2) and the third shaft(4) is configured with at least a third partial transmission ratio (i3),the first power branch (P1) has a first control element (S6) forconnecting the first power branch (P1) to a power flow at the firstpartial transmission ratio (i1), the second power branch (P2) has asecond control element (S5) for connecting the second power branch (P2)to a power flow at the second partial transmission ratio (i2), and thethird power branch (P3) has a third control element (S1) for connectingthe third power branch (P1) to a power flow at the first partialtransmission ratio (i3), and at least one of the second and third shafts(3, 4) of the planetary gearset (5) interacting with an additionalcontrol element (S2, S4), via which the at least one of the second andthird shafts (3, 4) can be supported in relation to a housing (6) and athird additional control element (S3), the third additional controlelement (S3), in a closed state, blocks the planetary gearset (5), beingarranged between the second and third shafts (3, 4) of the planetarygearset (5), the transmission (1) having nine forward gears.
 15. Thetransmission according to claim 13, wherein the third control element(S1) is provided in the third power branch (P3); the second controlelement (S5) in the second power branch (P2); the first control element(S6) in the first power branch (P1); the third shaft (4) of theplanetary gearset (5) is supported on the housing (6) by means of afirst additional control element (S2); the second shaft (3) of theplanetary gearset (5) is supported by means of a second additionalcontrol element (S4); and the third control element (S3) is providedbetween the second and third shafts (3, 4) of the planetary gearset (5).16. The transmission according to claim 13, wherein for shifting thefirst forward gear, the second additional and the first control elements(S4, S6) are closed; for shifting the second forward gear, the thirdadditional and the first control elements (S3, S6) are closed; forshifting the third forward gear, the second and the first controlelements (S5, S6) are closed; for shifting the fourth forward gear, thethird additional and the second control elements (S3, S5) are closed;for shifting the fifth forward gear, the third and the first controlelements (S1, S6) are closed; for shifting the sixth forward gear, thethird control element (S1) and the third additional control element (S3)are closed; for shifting the seventh forward gear, the third and secondcontrol elements (S1, S5) are closed; and for shifting the eighthforward gear, the third control element (S1) and the second additionalcontrol element (S4) are closed.
 17. The transmission according to claim14, wherein for shifting the first forward gear, the first additionaland the first control elements (S2, S6) are closed; for shifting thesecond forward gear, the second additional and the first controlelements (S4, S6) are closed; for shifting the third forward gear, thethird additional and the first control elements (S3, S6) are closed; forshifting the fourth forward gear, the second and the first controlelements (S5, S6) are closed; for shifting the fifth forward gear, thethird additional and the second control elements (S3, S5) are closed;for shifting the sixth forward gear, the third and the first controlelements (S1, S6) are closed; for shifting the seventh forward gear, thethird control element (S1) and third additional control element (S1, S3)are closed; for shifting the eighth forward gear, the third and thesecond control elements (S1, S5) are closed; and for shifting the ninthforward gear, the third control element (S1) and the second additionalcontrol element (S1, S4) are closed.
 18. The transmission according toclaim 13, wherein for shifting a reverse gear the first additional andthe second control elements (S2, S5) are closed.